With 2 it dropped to about 13.5. Don't know why. I know electronically it makes no sense but it did. Plus I like to park and play it at parties. With 3 it could play a lot longer.
You can never over do electrical. And what they say on the website is the bare minimum. I'd run the biggest possible alternator and 3 group 31 batteries and a group 34 plus 3 runs of 0 gauge.